ISSN Online: 2379-1748
ISBN Flash Drive: 978-1-56700-469-4
ISBN Online: 978-1-56700-470-0
Second Thermal and Fluids Engineering Conference
DRAG REDUCTION IN TURBULENT CHANNEL FLOW WITH TWO-TIERED SUPERHYDROPHOBIC WALLS
Аннотация
Drag reduction measurements are made in a channel with micro-structured superhydrophobic walls in combination
with larger scale turbulence reducing riblets. Pressure drop and PIV measurements across surfaces
exhibiting superhydrophobicity, riblets, and hybrid surfaces with both drag reducing mechanisms are presented.
Micro-ribs etched in silicon and coated with Teflon provide superhydrophobicity. Larger scale riblets
are deposited every 200 microns and extend nearly 100 microns above the ribs effectively dampening spanwise
turbulence. PIV measurements are used to explore velocity and shear stress profiles where one channel
wall is composed of a structured test surface and the other is smooth. These profiles allow estimation of friction
factors and overall drag reduction. Reynolds numbers ranging from 3.5 × 103 to 2.3 × 104 are explored. A modest drag reduction was observed for the riblet only surfaces but the hybrid surfaces composed of both micro-ribs and riblets show the greatest drag reduction.